@shyamcanvas1992,
As you are updating dataPoints by reading JSON every second, the chart gets updated with a new set of dataPoints that are being passed at every 1 second. You are unable to see updated datapoints in the chart as the JSON file itself is not updated. Please take a look at our documentation page for an example on Live Updating Charts from JSON API & AJAX.
—
Shashi Ranjan
Team CanvasJS